java.io.IOException: HTTP request failed, HTTP status: 500 SOAP Service

While I call web service from my android  app, I have an error.


 java.io.IOException: HTTP request failed, HTTP status: 500

 in my android app, I use ksoap lib.

I use php to test the service to know the service return true result.

<?php

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
require_once('lib/nusoap.php');

$client = new nusoap_client('http://****.com/index.php?wsdl', true);


$result = $client->call('get_authors', array('ID' => '193'));


echo $result;
 ?>


And the service return null.

So fix again the service and the error on android app disapear. ^^